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/* * Written by Doug Lea with assistance from members of JCP JSR-166 * Expert Group and released to the public domain, as explained at * http://creativecommons.org/licenses/publicdomain *///from ww w .j a v a 2s . com package com.nostra13.universalimageloader.core.deque; import java.util.Iterator; import java.util.concurrent.BlockingQueue; import java.util.concurrent.TimeUnit; /** * A {@link Deque} that additionally supports blocking operations that wait * for the deque to become non-empty when retrieving an element, and wait for * space to become available in the deque when storing an element. * * <p><tt>BlockingDeque</tt> methods come in four forms, with different ways * of handling operations that cannot be satisfied immediately, but may be * satisfied at some point in the future: * one throws an exception, the second returns a special value (either * <tt>null</tt> or <tt>false</tt>, depending on the operation), the third * blocks the current thread indefinitely until the operation can succeed, * and the fourth blocks for only a given maximum time limit before giving * up. These methods are summarized in the following table: * * <p> * <table BORDER CELLPADDING=3 CELLSPACING=1> * <tr> * <td ALIGN=CENTER COLSPAN = 5> <b>First Element (Head)</b></td> * </tr> * <tr> * <td></td> * <td ALIGN=CENTER><em>Throws exception</em></td> * <td ALIGN=CENTER><em>Special value</em></td> * <td ALIGN=CENTER><em>Blocks</em></td> * <td ALIGN=CENTER><em>Times out</em></td> * </tr> * <tr> * <td><b>Insert</b></td> * <td>{@link #addFirst addFirst(e)}</td> * <td>{@link #offerFirst offerFirst(e)}</td> * <td>{@link #putFirst putFirst(e)}</td> * <td>{@link #offerFirst offerFirst(e, time, unit)}</td> * </tr> * <tr> * <td><b>Remove</b></td> * <td>{@link #removeFirst removeFirst()}</td> * <td>{@link #pollFirst pollFirst()}</td> * <td>{@link #takeFirst takeFirst()}</td> * <td>{@link #pollFirst(long, java.util.concurrent.TimeUnit) pollFirst(time, unit)}</td> * </tr> * <tr> * <td><b>Examine</b></td> * <td>{@link #getFirst getFirst()}</td> * <td>{@link #peekFirst peekFirst()}</td> * <td><em>not applicable</em></td> * <td><em>not applicable</em></td> * </tr> * <tr> * <td ALIGN=CENTER COLSPAN = 5> <b>Last Element (Tail)</b></td> * </tr> * <tr> * <td></td> * <td ALIGN=CENTER><em>Throws exception</em></td> * <td ALIGN=CENTER><em>Special value</em></td> * <td ALIGN=CENTER><em>Blocks</em></td> * <td ALIGN=CENTER><em>Times out</em></td> * </tr> * <tr> * <td><b>Insert</b></td> * <td>{@link #addLast addLast(e)}</td> * <td>{@link #offerLast offerLast(e)}</td> * <td>{@link #putLast putLast(e)}</td> * <td>{@link #offerLast offerLast(e, time, unit)}</td> * </tr> * <tr> * <td><b>Remove</b></td> * <td>{@link #removeLast() removeLast()}</td> * <td>{@link #pollLast() pollLast()}</td> * <td>{@link #takeLast takeLast()}</td> * <td>{@link #pollLast(long, java.util.concurrent.TimeUnit) pollLast(time, unit)}</td> * </tr> * <tr> * <td><b>Examine</b></td> * <td>{@link #getLast getLast()}</td> * <td>{@link #peekLast peekLast()}</td> * <td><em>not applicable</em></td> * <td><em>not applicable</em></td> * </tr> * </table> * * <p>Like any {@link java.util.concurrent.BlockingQueue}, a <tt>BlockingDeque</tt> is thread safe, * does not permit null elements, and may (or may not) be * capacity-constrained. * * <p>A <tt>BlockingDeque</tt> implementation may be used directly as a FIFO * <tt>BlockingQueue</tt>. The methods inherited from the * <tt>BlockingQueue</tt> interface are precisely equivalent to * <tt>BlockingDeque</tt> methods as indicated in the following table: * * <p> * <table BORDER CELLPADDING=3 CELLSPACING=1> * <tr> * <td ALIGN=CENTER> <b><tt>BlockingQueue</tt> Method</b></td> * <td ALIGN=CENTER> <b>Equivalent <tt>BlockingDeque</tt> Method</b></td> * </tr> * <tr> * <td ALIGN=CENTER COLSPAN = 2> <b>Insert</b></td> * </tr> * <tr> * <td>{@link #add add(e)}</td> * <td>{@link #addLast addLast(e)}</td> * </tr> * <tr> * <td>{@link #offer offer(e)}</td> * <td>{@link #offerLast offerLast(e)}</td> * </tr> * <tr> * <td>{@link #put put(e)}</td> * <td>{@link #putLast putLast(e)}</td> * </tr> * <tr> * <td>{@link #offer offer(e, time, unit)}</td> * <td>{@link #offerLast offerLast(e, time, unit)}</td> * </tr> * <tr> * <td ALIGN=CENTER COLSPAN = 2> <b>Remove</b></td> * </tr> * <tr> * <td>{@link #remove() remove()}</td> * <td>{@link #removeFirst() removeFirst()}</td> * </tr> * <tr> * <td>{@link #poll() poll()}</td> * <td>{@link #pollFirst() pollFirst()}</td> * </tr> * <tr> * <td>{@link #take() take()}</td> * <td>{@link #takeFirst() takeFirst()}</td> * </tr> * <tr> * <td>{@link #poll(long, java.util.concurrent.TimeUnit) poll(time, unit)}</td> * <td>{@link #pollFirst(long, java.util.concurrent.TimeUnit) pollFirst(time, unit)}</td> * </tr> * <tr> * <td ALIGN=CENTER COLSPAN = 2> <b>Examine</b></td> * </tr> * <tr> * <td>{@link #element() element()}</td> * <td>{@link #getFirst() getFirst()}</td> * </tr> * <tr> * <td>{@link #peek() peek()}</td> * <td>{@link #peekFirst() peekFirst()}</td> * </tr> * </table> * * <p>Memory consistency effects: As with other concurrent * collections, actions in a thread prior to placing an object into a * {@code BlockingDeque} * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a> * actions subsequent to the access or removal of that element from * the {@code BlockingDeque} in another thread. * * <p>This interface is a member of the * <a href="{@docRoot}/../technotes/guides/collections/index.html"> * Java Collections Framework</a>. * * @since 1.6 * @author Doug Lea * @param <E> the type of elements held in this collection */ public interface BlockingDeque<E> extends BlockingQueue<E>, Deque<E> { /* * We have "diamond" multiple interface inheritance here, and that * introduces ambiguities. Methods might end up with different * specs depending on the branch chosen by javadoc. Thus a lot of * methods specs here are copied from superinterfaces. */ /** * Inserts the specified element at the front of this deque if it is * possible to do so immediately without violating capacity restrictions, * throwing an <tt>IllegalStateException</tt> if no space is currently * available. When using a capacity-restricted deque, it is generally * preferable to use {@link #offerFirst offerFirst}. * * @param e the element to add * @throws IllegalStateException {@inheritDoc} * @throws ClassCastException {@inheritDoc} * @throws NullPointerException if the specified element is null * @throws IllegalArgumentException {@inheritDoc} */ void addFirst(E e); /** * Inserts the specified element at the end of this deque if it is * possible to do so immediately without violating capacity restrictions, * throwing an <tt>IllegalStateException</tt> if no space is currently * available. When using a capacity-restricted deque, it is generally * preferable to use {@link #offerLast offerLast}. * * @param e the element to add * @throws IllegalStateException {@inheritDoc} * @throws ClassCastException {@inheritDoc} * @throws NullPointerException if the specified element is null * @throws IllegalArgumentException {@inheritDoc} */ void addLast(E e); /** * Inserts the specified element at the front of this deque if it is * possible to do so immediately without violating capacity restrictions, * returning <tt>true</tt> upon success and <tt>false</tt> if no space is * currently available. * When using a capacity-restricted deque, this method is generally * preferable to the {@link #addFirst addFirst} method, which can * fail to insert an element only by throwing an exception. * * @param e the element to add * @throws ClassCastException {@inheritDoc} * @throws NullPointerException if the specified element is null * @throws IllegalArgumentException {@inheritDoc} */ boolean offerFirst(E e); /** * Inserts the specified element at the end of this deque if it is * possible to do so immediately without violating capacity restrictions, * returning <tt>true</tt> upon success and <tt>false</tt> if no space is * currently available. * When using a capacity-restricted deque, this method is generally * preferable to the {@link #addLast addLast} method, which can * fail to insert an element only by throwing an exception. * * @param e the element to add * @throws ClassCastException {@inheritDoc} * @throws NullPointerException if the specified element is null * @throws IllegalArgumentException {@inheritDoc} */ boolean offerLast(E e); /** * Inserts the specified element at the front of this deque, * waiting if necessary for space to become available. * * @param e the element to add * @throws InterruptedException if interrupted while waiting * @throws ClassCastException if the class of the specified element * prevents it from being added to this deque * @throws NullPointerException if the specified element is null * @throws IllegalArgumentException if some property of the specified * element prevents it from being added to this deque */ void putFirst(E e) throws InterruptedException; /** * Inserts the specified element at the end of this deque, * waiting if necessary for space to become available. * * @param e the element to add * @throws InterruptedException if interrupted while waiting * @throws ClassCastException if the class of the specified element * prevents it from being added to this deque * @throws NullPointerException if the specified element is null * @throws IllegalArgumentException if some property of the specified * element prevents it from being added to this deque */ void putLast(E e) throws InterruptedException; /** * Inserts the specified element at the front of this deque, * waiting up to the specified wait time if necessary for space to * become available. * * @param e the element to add * @param timeout how long to wait before giving up, in units of * <tt>unit</tt> * @param unit a <tt>TimeUnit</tt> determining how to interpret the * <tt>timeout</tt> parameter * @return <tt>true</tt> if successful, or <tt>false</tt> if * the specified waiting time elapses before space is available * @throws InterruptedException if interrupted while waiting * @throws ClassCastException if the class of the specified element * prevents it from being added to this deque * @throws NullPointerException if the specified element is null * @throws IllegalArgumentException if some property of the specified * element prevents it from being added to this deque */ boolean offerFirst(E e, long timeout, TimeUnit unit) throws InterruptedException; /** * Inserts the specified element at the end of this deque, * waiting up to the specified wait time if necessary for space to * become available. * * @param e the element to add * @param timeout how long to wait before giving up, in units of * <tt>unit</tt> * @param unit a <tt>TimeUnit</tt> determining how to interpret the * <tt>timeout</tt> parameter * @return <tt>true</tt> if successful, or <tt>false</tt> if * the specified waiting time elapses before space is available * @throws InterruptedException if interrupted while waiting * @throws ClassCastException if the class of the specified element * prevents it from being added to this deque * @throws NullPointerException if the specified element is null * @throws IllegalArgumentException if some property of the specified * element prevents it from being added to this deque */ boolean offerLast(E e, long timeout, TimeUnit unit) throws InterruptedException; /** * Retrieves and removes the first element of this deque, waiting * if necessary until an element becomes available. * * @return the head of this deque * @throws InterruptedException if interrupted while waiting */ E takeFirst() throws InterruptedException; /** * Retrieves and removes the last element of this deque, waiting * if necessary until an element becomes available. * * @return the tail of this deque * @throws InterruptedException if interrupted while waiting */ E takeLast() throws InterruptedException; /** * Retrieves and removes the first element of this deque, waiting * up to the specified wait time if necessary for an element to * become available. * * @param timeout how long to wait before giving up, in units of * <tt>unit</tt> * @param unit a <tt>TimeUnit</tt> determining how to interpret the * <tt>timeout</tt> parameter * @return the head of this deque, or <tt>null</tt> if the specified * waiting time elapses before an element is available * @throws InterruptedException if interrupted while waiting */ E pollFirst(long timeout, TimeUnit unit) throws InterruptedException; /** * Retrieves and removes the last element of this deque, waiting * up to the specified wait time if necessary for an element to * become available. * * @param timeout how long to wait before giving up, in units of * <tt>unit</tt> * @param unit a <tt>TimeUnit</tt> determining how to interpret the * <tt>timeout</tt> parameter * @return the tail of this deque, or <tt>null</tt> if the specified * waiting time elapses before an element is available * @throws InterruptedException if interrupted while waiting */ E pollLast(long timeout, TimeUnit unit) throws InterruptedException; /** * Removes the first occurrence of the specified element from this deque. * If the deque does not contain the element, it is unchanged. * More formally, removes the first element <tt>e</tt> such that * <tt>o.equals(e)</tt> (if such an element exists). * Returns <tt>true</tt> if this deque contained the specified element * (or equivalently, if this deque changed as a result of the call). * * @param o element to be removed from this deque, if present * @return <tt>true</tt> if an element was removed as a result of this call * @throws ClassCastException if the class of the specified element * is incompatible with this deque (optional) * @throws NullPointerException if the specified element is null (optional) */ boolean removeFirstOccurrence(Object o); /** * Removes the last occurrence of the specified element from this deque. * If the deque does not contain the element, it is unchanged. * More formally, removes the last element <tt>e</tt> such that * <tt>o.equals(e)</tt> (if such an element exists). * Returns <tt>true</tt> if this deque contained the specified element * (or equivalently, if this deque changed as a result of the call). * * @param o element to be removed from this deque, if present * @return <tt>true</tt> if an element was removed as a result of this call * @throws ClassCastException if the class of the specified element * is incompatible with this deque (optional) * @throws NullPointerException if the specified element is null (optional) */ boolean removeLastOccurrence(Object o); // *** BlockingQueue methods *** /** * Inserts the specified element into the queue represented by this deque * (in other words, at the tail of this deque) if it is possible to do so * immediately without violating capacity restrictions, returning * <tt>true</tt> upon success and throwing an * <tt>IllegalStateException</tt> if no space is currently available. * When using a capacity-restricted deque, it is generally preferable to * use {@link #offer offer}. * * <p>This method is equivalent to {@link #addLast addLast}. * * @param e the element to add * @throws IllegalStateException {@inheritDoc} * @throws ClassCastException if the class of the specified element * prevents it from being added to this deque * @throws NullPointerException if the specified element is null * @throws IllegalArgumentException if some property of the specified * element prevents it from being added to this deque */ boolean add(E e); /** * Inserts the specified element into the queue represented by this deque * (in other words, at the tail of this deque) if it is possible to do so * immediately without violating capacity restrictions, returning * <tt>true</tt> upon success and <tt>false</tt> if no space is currently * available. When using a capacity-restricted deque, this method is * generally preferable to the {@link #add} method, which can fail to * insert an element only by throwing an exception. * * <p>This method is equivalent to {@link #offerLast offerLast}. * * @param e the element to add * @throws ClassCastException if the class of the specified element * prevents it from being added to this deque * @throws NullPointerException if the specified element is null * @throws IllegalArgumentException if some property of the specified * element prevents it from being added to this deque */ boolean offer(E e); /** * Inserts the specified element into the queue represented by this deque * (in other words, at the tail of this deque), waiting if necessary for * space to become available. * * <p>This method is equivalent to {@link #putLast putLast}. * * @param e the element to add * @throws InterruptedException {@inheritDoc} * @throws ClassCastException if the class of the specified element * prevents it from being added to this deque * @throws NullPointerException if the specified element is null * @throws IllegalArgumentException if some property of the specified * element prevents it from being added to this deque */ void put(E e) throws InterruptedException; /** * Inserts the specified element into the queue represented by this deque * (in other words, at the tail of this deque), waiting up to the * specified wait time if necessary for space to become available. * * <p>This method is equivalent to * {@link #offerLast offerLast}. * * @param e the element to add * @return <tt>true</tt> if the element was added to this deque, else * <tt>false</tt> * @throws InterruptedException {@inheritDoc} * @throws ClassCastException if the class of the specified element * prevents it from being added to this deque * @throws NullPointerException if the specified element is null * @throws IllegalArgumentException if some property of the specified * element prevents it from being added to this deque */ boolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException; /** * Retrieves and removes the head of the queue represented by this deque * (in other words, the first element of this deque). * This method differs from {@link #poll poll} only in that it * throws an exception if this deque is empty. * * <p>This method is equivalent to {@link #removeFirst() removeFirst}. * * @return the head of the queue represented by this deque * @throws java.util.NoSuchElementException if this deque is empty */ E remove(); /** * Retrieves and removes the head of the queue represented by this deque * (in other words, the first element of this deque), or returns * <tt>null</tt> if this deque is empty. * * <p>This method is equivalent to {@link #pollFirst()}. * * @return the head of this deque, or <tt>null</tt> if this deque is empty */ E poll(); /** * Retrieves and removes the head of the queue represented by this deque * (in other words, the first element of this deque), waiting if * necessary until an element becomes available. * * <p>This method is equivalent to {@link #takeFirst() takeFirst}. * * @return the head of this deque * @throws InterruptedException if interrupted while waiting */ E take() throws InterruptedException; /** * Retrieves and removes the head of the queue represented by this deque * (in other words, the first element of this deque), waiting up to the * specified wait time if necessary for an element to become available. * * <p>This method is equivalent to * {@link #pollFirst(long, java.util.concurrent.TimeUnit) pollFirst}. * * @return the head of this deque, or <tt>null</tt> if the * specified waiting time elapses before an element is available * @throws InterruptedException if interrupted while waiting */ E poll(long timeout, TimeUnit unit) throws InterruptedException; /** * Retrieves, but does not remove, the head of the queue represented by * this deque (in other words, the first element of this deque). * This method differs from {@link #peek peek} only in that it throws an * exception if this deque is empty. * * <p>This method is equivalent to {@link #getFirst() getFirst}. * * @return the head of this deque * @throws java.util.NoSuchElementException if this deque is empty */ E element(); /** * Retrieves, but does not remove, the head of the queue represented by * this deque (in other words, the first element of this deque), or * returns <tt>null</tt> if this deque is empty. * * <p>This method is equivalent to {@link #peekFirst() peekFirst}. * * @return the head of this deque, or <tt>null</tt> if this deque is empty */ E peek(); /** * Removes the first occurrence of the specified element from this deque. * If the deque does not contain the element, it is unchanged. * More formally, removes the first element <tt>e</tt> such that * <tt>o.equals(e)</tt> (if such an element exists). * Returns <tt>true</tt> if this deque contained the specified element * (or equivalently, if this deque changed as a result of the call). * * <p>This method is equivalent to * {@link #removeFirstOccurrence removeFirstOccurrence}. * * @param o element to be removed from this deque, if present * @return <tt>true</tt> if this deque changed as a result of the call * @throws ClassCastException if the class of the specified element * is incompatible with this deque (optional) * @throws NullPointerException if the specified element is null (optional) */ boolean remove(Object o); /** * Returns <tt>true</tt> if this deque contains the specified element. * More formally, returns <tt>true</tt> if and only if this deque contains * at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. * * @param o object to be checked for containment in this deque * @return <tt>true</tt> if this deque contains the specified element * @throws ClassCastException if the class of the specified element * is incompatible with this deque (optional) * @throws NullPointerException if the specified element is null (optional) */ public boolean contains(Object o); /** * Returns the number of elements in this deque. * * @return the number of elements in this deque */ public int size(); /** * Returns an iterator over the elements in this deque in proper sequence. * The elements will be returned in order from first (head) to last (tail). * * @return an iterator over the elements in this deque in proper sequence */ Iterator<E> iterator(); // *** Stack methods *** /** * Pushes an element onto the stack represented by this deque. In other * words, inserts the element at the front of this deque unless it would * violate capacity restrictions. * * <p>This method is equivalent to {@link #addFirst addFirst}. * * @throws IllegalStateException {@inheritDoc} * @throws ClassCastException {@inheritDoc} * @throws NullPointerException if the specified element is null * @throws IllegalArgumentException {@inheritDoc} */ void push(E e); }